Ultra high frequency electron discharge device system



ULTRA HIGH FREQUENCY ELECTRON DISCHARGE DEVICE SYSTEM Filed July 7, 1942ANTENNA You/HE 0F ODULA TIA/o 0 TENT/14L s INVENTOR ATTO R N EY W. VANB, magma 2,404,745 I Patented July 23, 1946 UNITED STATES PATENT OFFICEULTRA HIGH FREQUENCY ELECTRON DISCHARGE DEVICE SYSTEM Walter van B.Roberts, Princeton, N. J assignor to Radio Corporation of America, acorporation of Delaware Application July 7, 1942, Serial No. 450,006

serves both as an antenna and as a control element for the electrondischarge device circuit.

In conventional transmitters, whether of the master oscillator poweramplification type or a simple oscillator type, it is the practice toemploy a final plate tank circuit having as little losses as possible,and to couple an antenna system to the plate tank circuit to obtainpower therefrom. Usually, a, resonant antenna system located at somedistance from the transmitter is used and connected to the transmitterby a transmission line which is preferably non-resonant. In such asystem there is at least one other resonant circuit, namely the antennasystem, to be properly tuned, besides the tank circuit. When very shortwaves are employed, however, it is often undesirable to use a longtransmission line and hence the oscillator system is located very closeto the radiating element in order to reduce the length of line required.But when the oscillator is kept so close to the radiator, there is nolonger any particular advantage in having the two structures, eachdesigned solely for its particular function, and in accordance with thepresent invention a single structure is employed which acts both as anoscillator tank and as a radiator and which may be arranged to permitsimple adjustment of the loading of the oscillator tank circuit withoutsubstantial effect upon the natural frequency thereof.

Accordingly, one of the objects of the present invention is to provide asimplified ultra short wave electron discharge devicetransmitter systemwherein a single tank circuit can act both as an oscillatory tunedcircuit for controlling the frequency of an electron discharge devicegenand as a resonant input circuit for an electron discharge device.

A more detailed description of the invention follows in conjunction withthe drawing, wherein: Fig. lshows a conventional type of transmittercircuit;

Figs. 2, 3 and 4 illustrate different electron discharge deviceembodiments of the present invention, for use particularly at ultra highfrequencies; and

Fig. 5 is a cross-section of Fig. 4 along line 55.

Fig. 1 shows a conventional type of high frequency oscillator employinga vacuum' tube V which has associated therewith a tuned circuit in theform of a pair of parallel rods A and B each eifectively one-quarter ofa wavelength long.

A separate dipole antenna ANT is connected by means of line X andcoupling coil L to the oscillator tank A, B. The rods A, B are connectedtogether at one end through radio frequency bypass and blockingcondensers C1, C2. The cathode of tube V is connected to the junctionpoint of condenser C1, C2 and to ground. The grid and plate electrodesof tube V are respectively connected to rods A and B. A grid-biasresistor R is provided to maintain the grid at a desired neg. ativepotential with respect to the cathode, and a choke coil CH is providedbetween one end of the conductor B (as shown) and a lead extending tothe positive terminal of a source of unidirectional potential HT. Thissource HT may be placed at any suitable location, usually near theelectron discharge device equipment, while the antenna may be moreremotely connected, let us say on the roof of a building. The points ofconnection between the grid and plate electrodes of the vacuum tube Vand the conductors A and B of the tank circuit, are so chosen as tomatch the impedance of the vacuum tube electrodes to the impedance ofthe tuned line tank circuit as much as possible. In the absence ofcoupling to the antenna, the tank A, B has very low losses as radiationfrom the two rods is, to a large extent, cancelled out, since thecurrents in these rods are in opposite directions.

According to the invention, there is eliminated the need for using aseparate antenna system with its associated transmission line and.coupling elements. This is done by so arranging the main oscillatorytank circuit that it functions both as a control element for the vacuumtub circuit and also as an antenna system. One such arrangement of theinvention is shown in Fig. 2, wherein the rods A and B are separated, asby bending, to prevent the cancellation of radiation to the extentobtained in the conventional system of Fig. 1. By means of such aseparation, there is obtained a much increased radiation resistance, andif the two rods A, B constituting the tank circuit are bent sufficientlyfar apart, the radiation loss may be made sufiiciently large to load theoscillator be located on the roof of a building while the source ofpolarizing potentia'h aswell as the 'signal modulating apparatus, may"be located at some distance removed from the generator and radiator,with the connecting leads'betwen' them devoid of high frequencycurrents.

Fig. 3 illustrates another embodiment of "the invention, whereinthe-tank circuit is composed of rods A" and B each-of which has a length'equalto a quarter of the length of the operating wave and connected atone end to 'the grid and plate electrodes of the vacuum tube V-thrOughsuitable radio frequency by-pass and blocking condensers'Ci, Cg.Rods'Aand B are shown pivoted at points P, P intermediate their ends,

preferably near the center of the tank circuit,

for enabling the rods *A'QB' of the tank to'be separatedito any desireddegree. This is done by means of'a handle H locatedat theend of theparallel-rod tankremoved from the vacuum tube.

In one position the rods of the'tank circuit can "be paral1e1 to eachother, as shownqin dotted lines, in which casethere will bevery littleradiation from the tank circuit because of cancellation due to thecurrents in the rods flowing in opposite directions. TheradiationTesistarice of the tank cirCuitLis increasedby pulling the rodsA, B" apart by 'applying'pressure to the handle H. The pivots P,Penable'these rods to be pulled apart Without bending, as shown. Itshould be noted that'the grid and plate electrodes of the vacuum tube Vare connected togpoints of high voltage on the tankcircuitlj".Thisiarrangement f thus enables the radiation resistance tobe increased to provide proper loading for the oscillator tube V withoutsubstantially affecting the frequency of (oscillation which "isdetermined mostly by the total Ie'ngthof the tank circuit between thegrid and plate electrodes. f

-Fig. 4 shows another embodiment of the iinvention which gives .a irnoresymmetricallradiation pattern. In this figure,1A" is the inner-conductorof a concentricline tank whose .outer conductor is B".. TheconductorsA'i, B'Kare connected together atone end by a metallic endplate D. The outer conductor may be of square cross section,

so that a portion, at least (the 'open-ended upper portion), of theouter conductor maybe arranged Although it should be. noted thatithegrid is connected to a desired point .of'radio frequency potentiallonthe "inner conductorjthrough a radioifrequen'cy bypass condenser C3,while the platej'fis"c0nnected, to 'ground'ifrom a radio frequencystandpoint to the generator.

through a radio frequency by-pass condenser C4, and the cathode isconnected to a point of intermediate frequency potential. This is doneby connecting the plate to the outer surface of the outer conductor (asshown), while the grid and cathode leads extend through apertures ondifferent points of the inner conductor to suitable bias and heatingsources. A transformer TR shows one way of applying modulatingpotentials The modulation can als be effected, alternatively, ifdesired, by means of key K which is in shunt to a portion R of the gridbias resistance.

f Fig. 5 is a plan view of the tank circuit of Fig. 4 along the line 5,.5 and is given to more clearly illustrate the configuration of the tankcircuit when .it-is swung open.

Although Figs. 2, 3 and 4 have been described above in connection withtransmitter arrangements, it should be understood that, if desired, thesame systems can be used 'for receiving punposes, in which case thevacuum tube will actas a detector by suitably choosing the proper .biasand polarizing potentials for the grid and plate electrodes. q

In all of Figs. 2, 3 and 4 of the invention, it-

.should be observed that a unitary structure having only a singlefundamental resonance frequency is provided so that there is nopossibility of any tuning adjustments being required except for thepurpose of deliberately changing the frequency of the tank circuit. -Forvery short waves, therefore, such that the combined oscillator andradiator must be physically close together in any case, there isobtained the-advantage that only the unavoidable losses of the singleresonant system need be subtracted from the useful vacuum tube outputpower. Another advantage is that the adjustment of the radiatingoscillator is greatly simplified in that the loading may be adjusted bya single adjustment which does not seriously affect the frequency, andno tuning adjustment need be'made on the radiating system except for thepurposeof fine adjustment of the frequency. a 3

What is claimed is: a a

1. An ultra short wave system comprising a multieelectrode electrondischarge device including grid and plate electrodes, a singlemultirelement electrical resonant structure whose dimensions around saidstructure along the path of oscillatory current flow therein ..are suchas to produce a desired oscillation frequency, the spacingbetween saidelements being adjusted to give a desired coupling to the ethertothereby cause said structure to act as an antenna, leads regenerativelycoupling said electron discharge device-to said resonant structure, andmeansforlsupplying suitable bias and operating potentials to theelectrodes of said device to generate and radiate oscillations orregenerativelyreceive and detectoscillations, said resonant structurecomprising two I metallic rods connected. togetherat one end andconnected at the other end to the gridand. plate electrodes .of saidelectron discharge device, said metallic rodsbeing spaced furtherjapartatltheir centers than at their ends.

2. An ultra short wave system compri n a electron discharge devicehavinga, grid and a plate, a single multi-element elegtrical resonantquency, a lead coupling saidgrid to one element of said resonantstructure, another lead coupling said plate to another element of saidresonant structure, the spacing between said elements of said resonantstructure being adjusted to give a desired coupling to the ether tothereby cause said structur to act as an antenna, and means forsupplying suitable bias and operating potentials to the electrodes ofsaid devic to cause said device to generate and radiate oscillations orregeneratively receive and detect oscillations, said resonant structurecomprising a pair of conductors which are arranged parallel to eachother over a portion of their lengths and which diverge from each otherfor the remaining portion of their lengths.

3. An ultra short wave system comprising a multi-electrode electrondischarge device including grid and plate electrodes, a singlemultielement electrical resonant structure whose dimensions around saidstructure along the path of oscillatory current flow therein are such asto produce a desired oscillation frequency, the spacing between saidelements being adjusted to give a desired coupling to the ether tothereby cause said structure to act as an antenna, leads regenerativelycoupling said electron discharge device to said resonant structure, andmeans for supplying suitable bias and operating potentials to theelectrodes of said device to generate and radiate oscillations orregeneratively receive and detect oscillations, said resonant structurecomprising two metallic rods connected together at one end and connectedat the other end to the grid and plate electrodes of said electrondischarge device, said metallic rods being pivoted intermediate theirends and provided with means for spacing them further apart at thelocation of the pivots than at their ends.

4. An ultra short wave system comprising a multi-electrode electrondischarge device having grid and plate electrodes, a single tunedcircuit which serves both as a frequency controlling element and as anantenna, said tuned circuit consisting of a pair of conductors so spacedapart as to give a desired degree of coupling to the ether,

a low impedance connection between the grid' electrode of said electrondischarge device and one of said pair of conductors, another lowimpedance connection between the plate electrode of said electrondischarge device and the other conductor of said pair, and means forsupplying suitable bias and operating potentials to the electrodes ofsaid device to generate and radiate oscillations or regenerativelyreceive and detect oscillations.

5. A system in accordance with claim 2, including a turn-bucklearrangement for adjusting the degree of divergence of said rods.

6. An ultra short wave system comprising a multi-electrode electrondischarge device having a grid and a plate, a coaxial line resonantstructure whose dimensions around said structure along the path ofoscillatory current flow therein are such as to produce a desiredoscillation frequency, said coaxial line structure having inner andouter conductors which are connected together at one end from a radiofrequency standpoint and open at the other end, a connection from groundto said outer conductor, said inner and outer conductors being parallelto each other for a portion near the closed end and diverging from eachother an adjustable amount for a portion near the open end, the spacingbetween the inner and outer conductors being adjusted to give a desiredcoupling to the ether to thereby cause said structure to act as anantenna, leads regeneratively coupling said electron discharge device tosaid resonant structure including a connection between said grid and apoint onsaid inner conductor intermediate its ends and a connection oflow impedance to energy of the operating frequency coupling said plateto ground, and means for supplying suitable bias and operatingpotentials to the electrodes of said device to cause said device togenerate and radiate oscillations or regeneratively receive and detectoscillations.

WALTER VAN B. ROBERTS.

